Spinning cans--which are also variously known as receiving cans, depositing cans or feed boxes--are usually open ended, for example cylindrical, containers. The spinning cans may be arranged for uniform rotation about their axis and superimposed on or combined with the rotation of the can there may be a fluctuating "traversing" or reciprocating movement of the can or of a thread guide. A process of this kind has been disclosed for example in German Laid-Open Specification (DAS) No. 1 028 736 wherein a continuous thread or yarn is deposited in spiral shaped paths into a cake-like structure. Another process of the above general kind has been described in German Published Specification (DT-OS) No. 2 427 722.
It is known to arrange spinning can changing systems for at least partially automatic operation and this requires that in the changing of the cans the continuously fed filamentary yarns must also be automatically severed at the full can.
A number of solutions are known for this kind of problem. Thus, in German Published Patent Specification (DT-OS) No. 1 685 580 a device has been described in which, after the can has been completely filled, a depositing board or plate is shoved into the run of the fibers. An edge of this depositing board simultaneously serves as a severing device. The filamentary yarn fed during the can changing operation is collected on this depositing board. If an empty spinning can has been put in place in lieu of the full can, the depositing board is again shoved out of the fiber run and the yarns which have been piled up on the depositing board in the meantime, all drop into the can. A disadvantage of this device is that the severed yarn end drops into the full spinning can so that it can be retrieved only with great difficulty. A further drawback of the device resides in that in stripping off the material collected on the depositing board, entanglements may occur which may later, upon the drawing of the yarn from the can, lead to the formation of knots in the strand of yarn.
Also known is German Pat. No. (DT-PS) 1 091 010 in which the yarn is ruptured incident to its transfer from one can to the other. This, however, applies to yarns consisting of short, relatively loosely adhering fibers particularly natural fibers. In the case of filamentary yarns which consist of synthetic continuous fibers, this procedure is impossible.
Further known is Laid-Open German Patent Specification (DT-AS) No. 2 035 020 in which three cans are placed on a turntable. Between each of the cans there is provided a roof-shaped member in the form of a support element. In the rotational axis of the turntable there is provided a stationary outrigger arm or boom with a cutting off device in such a way that the arm does not impede the run of the yarn. During the can changing action the filamentary yarn comes to lie across the roof-shaped member due to the rotation of the turntable. After the changing operation has been completed, that is, when the empty can stands under the yarn feeding device the cutting off device is lowered onto the roof-shaped member and the yarn is severed. During the cutting operation the yarn is held by two spring-loaded clamping members respectively attached to the two sides of the cutting device. Thereupon the cutting off device is lifted again and during the final portion of the return stroke of the cutting device the two associated clamping members release the corresponding free ends of the yarn, thereby permitting them to drop back into the respective cans.
Here, too, it is disadvantageous that the severed filamentary yarn, that is, one end thereof, drops back into the filled can. Also, it is only subsequent to the lifting of the boom that the other end of the filamentary yarn is released and drops into the can, that is, at a time when this can is already being loaded and when several layers have already been fed into this can in the meantime; this may also lead to difficulties upon drawing off of the filamentary yarn from the can. Another drawback of this known cutting off and holding device is that it requires the cans to be guided in an arcuate path.